1. Field of the Invention
The present invention relates in general to the manufacture of semiconductor devices and, more particularly, to a method for efficiently and uniformly cleaning a chemical vapor deposition (CVD) chamber used in the manufacture of such devices.
2. Description of the Prior Art
Plasma reactors such as chemical vapor deposition (CVD) tools employed in deposition processing of semiconductor wafers tend to accumulate contaminants on the interior chamber surfaces. Such contamination occurs because the same material deposited on the substrate or wafer is also deposited on the interior chamber surfaces.
For instance, a high-density plasma chemical vapor deposition (HDPCVD) tool is commonly employed to deposit material layers such as silicon dioxide on a substrate. It is well known that over a period of use, the material layers form as deposits on the walls of a deposition chamber. The buildup of these material layer deposits is undesirable because the deposits can flake off from the interior surfaces of the deposition chamber and introduce defects into the substrate and overlying layers and decrease the uniformity of layers being deposited on the substrate and the overall quality of the device.
As the yield of functional devices produced from the chamber continues to decrease, it eventually becomes necessary to stop semiconductor device fabrication and replace the dome of the deposition chamber, thereby increasing the overall costs of semiconductor device fabrication.
To reduce the build-up of material layer deposits, the deposition chamber is periodically cleaned in situ, usually using a fluorine-containing cleaning gas, such as fluorine, nitrogen tri-fluoride (NF3) or hexafluoroethane (C2F6). Periodic in situ cleaning is typically done in-between chemical deposition procedures being performed on one or more batches of wafers. It is desired to provide a balance between efficient chamber cleaning in a minimum period and using a minimum amount of cleaning gas.
U.S. Pat. No. 6,584,987 filed Mar. 16, 2001 by Cheng et al. teaches a method for improved cleaning in HDPCVD process with reduced NF3 usage. The method disclosed in U.S. Pat. No. 6,584,987 includes the steps of providing argon/perfluorinated hydrocarbon plasma in a chamber to be cleaned; flowing oxygen gas into the chamber; maintaining the plasma in the chamber to elevate the temperature of the chamber; baking the chamber containing the plasma for a period of time; turning off the power to cease the plasma; evacuating the chamber; and flowing cleaning gas into the chamber to start normal cleaning procedure.
One drawback of this method is that additional gases such as oxygen and perfluorinated hydrocarbon are required. After baking the chamber and prior to the normal NF3 cleaning procedure, the gas mixture must be pumped out of the chamber. It is disadvantageous that the use of such cleaning gases in a baking step requires additional processing time thereby decreasing wafer throughput.
In light of the above, there is a need in this industry to provide an efficient in situ cleaning process that allows the production of semiconductor devices with low numbers of defects and thereby extending the time between dome changes of the deposition chamber. Further, it is desired to provide a uniform clean to the interior surfaces of the dome of the deposition chamber.